| Method |
Precise Learning Objective |
Linked |
Question / Activity
(Designed for maximum working out) |
Stepping Stones |
Pitstop Check
(Thinking Map) |
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Flame tests can be used to identify some metal ions (cations). Lithium, sodium, potassium, calcium and copper compounds produce distinctive colours in flame tests: ? lithium compounds result in a crimson flame
? sodium compounds result in a yellow flame
? potassium compounds result in a lilac flame
? calcium compounds result in an orange-red flame
? copper compounds result in a green flame.
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What are the different colours produced by some metal ions (cations)? Flame tests. |
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If a sample containing a mixture of ions is used some flame colours can be masked |
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When are some flame colours masked? |
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Carbonates react with dilute acids to form carbon dioxide gas. Carbon dioxide can be identified with limewater. |
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How do carbonates react with dilute acids? Students design a flow diagram on testing for positive ions. |
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Students should be able to identify species from the results of the tests in 4.8.3.1 to 4.8.3.5. |
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Halide ions in solution produce precipitates with silver nitrate solution in the presence of dilute nitric acid. Silver chloride is white, silver bromide is cream and silver iodide is yellow. |
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What do Halide ions produce when they react with silver nitrate solution? Students design a flow diagram on testing for negative ions. |
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Flame colours of other metal ions are not required knowledge. |
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SEPARATE EW
A group of students had four different colourless solutions in beakers 1, 2, 3 and 4,
The students knew that the solutions were
• sodium chloride
• sodium iodide
• sodium carbonate
• potassium carbonate
but did not know which solution was in each beaker.
Plan a method that could be used to identify each solution.
You may use the following reagents:
• dilute nitric acid
• silver nitrate solution.
It is suggested that a flame test is used to identify the positive ions.
Outline a method that could identify the four solutions.
You should include the results of the tests you describe. |
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